Growth Mechanism and Electronic Structure of Zn3P2 on the Ga-Rich GaAs(001) Surface

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• 作者：Seokmin Jeon ; Jeffrey P. Bosco ; Samantha S. Wilson ; Steve J. Rozeveld ; Hyungjun Kim ; Harry A. Atwater
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 19, 2014
• 年：2014
• 卷：118
• 期：24
• 页码：12717-12726
• 全文大小：642K
• 年卷期：v.118,no.24(June 19, 2014)
• ISSN：1932-7455

文摘

The growth of epitaxial Zn₃P₂ films on III鈥揤 substrates unlocks a promising pathway toward high-efficiency, earth-abundant photovoltaic devices fabricated on reusable, single-crystal templates. The detailed chemical, structural, and electronic properties of the surface and interface of pseudomorphic Zn₃P₂ epilayers grown on GaAs(001) were investigated using scanning tunneling microscopy/spectroscopy and high-resolution X-ray photoelectron spectroscopy. Two interesting features of the growth process were observed: (1) vapor-phase P₄ first reacts with the Ga-rich GaAs surface to form an interfacial GaP layer with a thickness of several monolayers, and (2) a P-rich amorphous overlayer is present during the entire film growth process, beneath which a highly ordered Zn₃P₂ crystalline phase is precipitated. These features were corroborated by transmission electron micrographs of the Zn₃P₂/GaAs interface as well as density functional theory calculations of P reactions with the GaAs surface. Finally, the valence-band offset between the crystalline Zn₃P₂ epilayer and the GaAs substrate was determined to be 螖E_V = 1.0 卤 0.1 eV, indicating the formation of a hole-depletion layer at the substrate surface which may inhibit formation of an ohmic contact.